After the engine was taken off to change the auto tranny and assembled back on, the car won't start or run on gas but it starts and runs well on LPG (bi-fuel).
According to my mechanic, there's no signal from ECU to injectors but ignition system works.
He also said that the car had this problem before so the PO sold this car. I bought it and had been using this car for 2 years without any engine issue.
My mechanic are having a headache now lol cuz he can't find out what to do.
What should we do?
If anyone knows what probably goes wrong with the car please give your opinion here. We really need advice.

Many Thanks,
Rob

crank sensor, perhaps.......?
is the ECU recording any error codes at all?

The crank sensor has been changed recently and I found that when it goes wrong, neither injectors nor spark plugs works.
Another thing is the ignition code (anti theft, 4-digit code) has been cancled so I never had to press the code when I started the engine.
Do you think this may be the problem?
Wheter it is or not, I'd like to ask how this thing works, and what will happen if the wrong code has been keyed.
Only injectors die or no signal to spark plugs also??

Regards,
Rob

What kind of lpg system is on it. Single or Multipoint?

V6 ecu's are know to die... You'll get a spark, but it wont deliver fuel as the ECU is not telling the injectors when to fire the fuel into the air stream ...

Try an ECU if you have a spare, or can get a spare one...


Rgds
Paul

I think it's called single point LPG system (called "Fixed Mixer" here, using vacuum, no LPG injectors).

Sadly, a V6 ECU is sooooooo... hard to find, there are very few V6 here in my country but it seems like I have to find it now.

Still want other suggestions.

Thanks,
Rob

Your lpg system must have a little box that stops the injectors firing and also makes the petrol ecu think they have. This should switch off when you switch the lpg off. You need to check that it is doing this. It must be doing what it should when running on lpg otherwise the petrol ecu would be displaying a fault saying that the petrol injectors weren't firing.

Hi Rob

Immobiliser is normally put out of use simply by unplugging the electrical connector while the engine is running. Once out of use the ECU recognises this and ignores it at each start up.

Regards

XMexc

Just came back from the shop.

I looked at the ignition code lights when I tried to start the engine, there was only a green light on.

The LPG switching box issue sounds nice to me cuz I don't need to pay for a ECU
I'll go check it out first as my plan A.

Plan B : I just found a part shop that may have a used ECU.
I plan to bring the car to that shop and try a spare one.

Plan C : My mechanic (another one) told me that there is an ECU repairing shop
not so far away from my area. I'll take the ECU there and see what they can do.

This forum is such a warm place for an XM owner like me. After this problem ends,
I want to share my experience of cheap strut top solution.
Here we use Xantia's strut tops (which are 5 times cheaper) with XMs by using a metal adapter and it works well.


Many Thanks,
Rob (from Citroen Club Thailand)

The 'lpg switching' box or Injector Emulator to gove it its correct name, may not be present, as it is only needed to prevent fault codes on the petrol ECU. Often the common feed to the injectors is isolated by the LPG system (sometimes the earlth sometimes +VE depending on the Petrol system) So you might not have one. Hoever it is worth looking at how the LPG isolates the injectors.

If your trip computer works then you have emulators fitted, is not or gives really odd readings then its not fitted

Stewart

My mechanic looked at the injector emulator today and he said that there's no signal from ECU coming to the injector emulator.

Tomorrow I'll go on my scary plan B.

Many thanks,
Rob

I tried another ECU today but nothing changed.

You say your mechanic had a look at the emulator and there was no signal. What was he looking for? I ask that because it's not a positive signal he is looking for. The injectors are all fed +V and individually earthed by the petrol ecu to fire them. Thus he is looking for a connection to earth. Are the injectors receiving +V? To test pull off a petrol injector connector, switch on the ignition and one of the wires should show +V.

I cannot think of anything worse than using a Xantia strut top on an Xm - must be some adaptation
too; from bitter experience I've found the metal in the Xantia tops is far thinner/inferior to an XM one!

The weight on the front end of a Xantia is less than an XM too, even where the same engine is used
so the design tolerances will be different!!

Andrew